The European Medicines Agency warned on Wednesday that vials of Roche's breast cancer drug Herceptin, thought to have been stolen from hospitals in Italy, have been tampered with and reintroduced into the supply chain. "Italian law enforcement authorities are currently investigating the theft and are looking at whether other medicines may also be affected," the agency said in a brief statement. So far there have been no reports that any harm has come to patients who may have been given the stolen drug, which was sold under false credentials.